X ray Enhancement of SN 1987A Due to Interaction with Its Ring-Like Nebula

摘要

The progenitor of the supernova 1987A, Sk-69 202 probably had lost a few solar-Min its stellar wind in the past evolutionary track from the red supergiant through the blue supergiant. A part of the mass is thought to form the ring-like nebula surrounding SN 1987A by the interaction with the faster wind in the later blue supergiant stage, and the other must be left outside the ring. In 10-20 yr after the explosion, the expanding ejecta will catch up and collide with the ring. Shocks due to the collision will propagate into and heat up the ejecta, the ring, and the matter outside. The shocked matter will be a thermal X-ray source of temperature of several times 10(exp 7) K, and the X-ray luminosity will reach (0.4-1)x10(exp 37) erg s(exp -1) for the ring of 0.03-0.08 solar-M. The X-ray emission will last for a few decades with luminosity higher than 10(exp 36) erg s(exp -1) depending also on the density outside the ring. We predict the X-ray spectrum as well as the light curve with hydrodynamical calculations taking into account the light travel effect and the opacity of the unshocked ejecta. The epoch of the flare-up depends on the mass inside the ring, and earlier X-ray observations can give a constraint. We give the relations of the mass with the epoch and the pre-flare luminosity in an analytical way based on the self-similar solutions with nonequipartition in the electron and the ion temperatures. Accordingly, the ROSAT observation in 1991 suggests the collision with the ring in 20 yr after the explosion.